The DPP method in which the offset of a tracking control signal resulting from lens shifting can be effectively suppressed has been in wide use as a tracking system for optical disks. In the method disclosed in JP-A 54415/1993, three spots for tracking, i.e. a main spot, a first sub-spot, and a second sub-spot are positioned being shifted by half a track pitch each on a land/groove disk or a groove recording disk, and the offset of the tracking control signal caused by lens shifting is, in principle, canceled based on calculations made using three push-pull signals detected. When the DPP method is used in an isolated optical system, there are cases in which optical axis deviation causes the magnitudes of the three push-pull signals to vary. A method aimed at solving the problem is disclosed in JP-A No. 89494/1993. In the method, gain adjustment is made, in a mirror section, between the push-pull signal of a main spot and the push-pull signals of sub-spots. In the method disclosed in JP-A No. 279659/2002, to make up for a difference in reflectivity between land and groove, distinction is made between land and groove and between media, and the push-pull signal of either sub-spot is selected for use. In the method disclosed in JP-A No. 320287/1995, a function for selecting the three-spot method or the DPP method according to the medium type is used.